Generally, a vacuum cleaner includes a bottom brush to draw in air and dust from the surface being cleaned, a motor driving chamber with a vacuum source, and a cyclone separating apparatus. The term “dust” will be used herein to refer collectively to dust, dirt, particulates, debris, contaminants, and other similar matter that can be entrained with the air suctioned by the vacuum cleaner.
After the air is drawn through the bottom brush, the cyclone separating apparatus is configured to whirl the dust-laden air, separate the dust from the air by centrifugal force, and then discharge the clean air via the motor driving chamber. Also, the vacuum cleaner can have a multi-cyclone separating apparatus instead of the cyclone separating apparatus.
The multi-cyclone separating apparatus has a main cyclone and one or more secondary cyclones. The main cyclone and the secondary cyclones separate dust from the air in two or more stages. An example of the conventional multi-cyclone dust separating apparatus is described in International Patent Publication Nos. WO 02/067755 and WO 02/067756, both by Dyson. However, the conventional multi-cyclone dust separating apparatus is arranged such that the downstream secondary cyclone is placed vertically with respect to the upstream main cyclone. Thus, the conventional multi-cyclone dust separating apparatus has a height more appropriate for an upright type cleaner but unsuitable for a canister type cleaner.
The overall height of the multi-cyclone dust separating apparatus can be reduced by placing the secondary cyclone near the outer circumference of the main cyclone as described in Korean Patent No. 554237. However, since shorter vacuum cleaners generally have smaller dust separating apparatuses, the user has to empty the dust separating apparatus more frequently.
To resolve the above problem, a multi-cyclone dust separating apparatus with increased dust holding capacity has been developed, as described in Korean Patent No. 648960. The multi-cyclone dust separating apparatus of Korean Patent No. 648960 reduces the overall height and thus can be used with both the upright type vacuum cleaner and the canister type vacuum cleaner. However, the multi-cyclone dust separating apparatus of Korean Patent No. 648960 continuously receives unfiltered air with small dust particles and is eventually affected by the dust. A suction motor causes air to pass sequentially through the main cyclone and a plurality of secondary cyclones. As the air passes through the cyclones, the dust is separated from the air and collected in a space defined at the lower portion of the separating apparatus. The air is then discharged directly, through an air discharge port, without passing through a separate filter. As a result, the suction motor continuously receives unfiltered air and is eventually affected by the dust.
Also, to increase the small dust filtering efficiency, a dust separating apparatus is provided with a filter, as described in Korean Patent Publication No. 2006-13855 and Korean Patent No. 623916. The dust separating apparatus of Korean Patent Publication No. 2006-13855 has a filter that is placed within the dust separating apparatus. The dust separating apparatus of Korean Patent No. 623916 has a filter that is screened by a grill which supports the filter, and the filter is inseparable from the dust separating apparatus. However, for both dust separating apparatuses, the filter is often blocked by large particles of dust. Thus, the filtering of small particles of dust deteriorates. Also, if the filter is blocked by dust, the suction motor becomes overloaded thereby shortening its lifespan. Accordingly, a user has to empty the dust separating apparatus more frequently which is inconvenient. Furthermore, the user is only able to determine the degree of contamination of the filter when the filter is removed. Because the filter has to be removed, the user has to handle a dirty filter which is unpleasant, or the user has to use a tool to handle the filter which is inconvenient. Also, if the filter is inserted in a relatively narrow space, it is not easy to remove or replace the filter.